For this purpose it is known to mount the picture to be reproduced on a suitable support, such as a slide holder, forwardly of a projection objective which coacts with condensing lens means, such as a pair of large-diameter field lenses, to produce an aerial image of the picture in an intermediate plane. With the foreground action taking part in or near that intermediate plane, an objective of a motion-picture camera focused upon that plane films the composite scene.
It is frequently desirable to vary the magnification ratio of the image so recorded on the motion-picture film. This can seemingly be accomplished by simply replacing an ordinary, fixed-focus camera objective with an object of the varifocal or zoom type; attempts to realize significant variations in the magfication ratio by this expedient have, however, been unsuccessful in the past. For reasons not fully understood heretofore, satisfactory image brightness could be achieved only over a small fraction of the zoom range.